Subgrade stabilization for fuel containment at Naval Base Point Loma 

Overview

The Naval Base Point Loma planned to construct eight fuel storage tanks on soft soil foundations. The design for these large-diameter tanks included stone column footings. To ensure safety in case of a fuel spill, cast-in-place containment dike walls were built around the tank farm. During the excavation of the dike wall footings, the contractor encountered soft pumping subgrade. Solmax was then consulted to provide a solution for stabilizing the subgrade. This modernization effort was crucial for maintaining the operational readiness of the U.S. Navy and other agencies that rely on DFSP Point Loma, including the U.S. Marine Corps Air Station Miramar and the U.S. Coast Guard.

Challenge

To address the subgrade stabilization at the Naval Base Point Loma, MIRAFI^® RS580i geotextile was placed directly on the soft pumping subgrade. This was followed by a 12-inch (30 cm) layer of 2-inch (5 cm) diameter crushed stone, which was spread using bulldozers and then compacted. Above this stone layer, a MIRAGRID 2XT biaxial geogrid was installed. An 8-inch (20 cm) section of crushed recycled concrete was then placed on the geogrid. Water was added to this crushed base material, and the entire section was compacted to create a tight foundation ready for the dike wall concrete footing.

This method ensured a stable and secure foundation for the containment dike walls, addressing the challenges posed by the soft subgrade and enhancing the overall safety and integrity of the fuel storage facility.

Solution

To address the subgrade stabilization at the Naval Base Point Loma, MIRAFI RS580i geotextile was utilized to eliminate the pumping subgrade condition. This high-performance geotextile provided superior tensile strength for subgrade support and effectively separated the pumping soils from the aggregate base. Additionally, it offered filtration and drainage of water from the pumping soils, as well as lateral confinement of the stone section. This stabilization method ensured a secure platform for the construction of the cast-in-place fuel containment dike walls, enhancing the overall safety and integrity of the fuel storage facility.